This device relates to a device for producing hollow bodies according to an internal high pressure metal forming process (IHU Process), and more particularly to such a device having an IHU-tool which is divided along a mold joint, the tool having an impression for receiving a tube-shaped blank, a press for opening and closing the IHU-tool, axially movable slides which are attached to an open end of the blank, working cylinders having piston rods to displace the slides axially, and a pair of pull rods which are assigned to the working cylinders to receive the reaction force between the IHU-tool and the working cylinder.
In the case of the device for producing hollow bodies according to the internal high pressure metal forming process (IHU Process) according to German Patent Document DE 41 03 078 C1, although the two pull rods of a pair are arranged at the same height with respect to one another and--viewed in the moving direction of the press toward the stationary tool part--on the right and left next to the piston rod of the working cylinder, they extend in a vertically offset manner with respect to the piston rod, that is, lower than the piston rod, specifically along the top side of the base plate carrying the shape-determining die and the working cylinders. In the case of the known device, by way of the above-mentioned slides, only the blank is closed on the face and the pressure medium is supplied, but an axial upsetting of the blank within the impression is not carried out. For this reason, the slides must only be pressed on by means of an axial force corresponding to the metal forming pressure and the cross-sectional surface of the blank.
A disadvantage in the case of the known device is the moment-loaded and non-exchangeable linking of the working cylinders to the pertaining shape-determining die. Because of the moment load of the pull rods during the pulling effect, for preventing unacceptably high tilting of the working cylinders, the pull rods and the working cylinders must be disposed along their whole length flatly on the above-mentioned base plate which, in turn, is supported on the press bed. Thus, the base plate and the press bed contribute to the relieving of moments of the linking of the working cylinders. However, they can only do so if the IHU-tool carrying the impression, including the working cylinders and their pull rod linking to the IHU-tool, each form a closed subassembly--as explicitly indicated--which, in its total course, rests flatly on the base plate and, after its adjustment, is fixedly screwed to it and which, in the case of a tool change, has to be exchanged as a whole. In addition, only horizontal positions of the working cylinders can be permitted in the different tools which are used alternately.
It is an object of the present invention to improve an IHU-tool in such a manner that arbitrary spatial positions of the working cylinders are possible and that, in the case of a tool change, only the die carrying the impression--in this case, called IHU-tool--has to be exchanged while the working cylinders remain in the device for producing hollow bodies or that the working cylinder/cylinders may be used on different dies.
These and other objects have been achieved according to the present invention by providing a device for producing a hollow body according to an internal high pressure metal forming process comprising a tool which is divided along a mold joint into a stationary tool part and a liftable tool part, the tool having an impression for receiving a tube-shaped blank, an end-side impression being assigned to an end of the blank, respectively, and being arranged approximately parallel to and centrally with respect to an end-side portion of the mold joint; a press which is movable in a direction transverse to the mold joint to open and close the tool; an axially movable slide which is arranged concentrically with respect to the end-side impression, respectively, and which is sealingly attached to an open end of the blank, a pressure medium being introduced into the blank via at least one slide; a hydraulic working cylinder which is arranged with a common axis as the end-side impression, respectively, and having a piston rod which holds the slide and which displaces the slide axially, the working cylinder being angularly and vertically adjustable on a support member; and a pair of pull rods which is assigned to the working cylinder, connecting the tool and the working cylinder with tensile strength in parallel to the common axis in order to receive a reaction force between the tool and the working cylinder, the pull rods of the pair being arranged on opposite sides of the piston rod at the same level as the piston rod, each pull rod extending into the end-side portion of the mold joint and being releasably anchored to each of the stationary tool part and the liftable tool part in a form-locking manner in corresponding recesses along the mold joint, the recesses configured such that after a working cycle the liftable tool part can be lifted away from the pull rod in a vertical direction without resistance.
The objects of the invention are also achieved according to another embodiment of the present invention in which each pull rod is releasably anchored to a holding wall in a form-locking manner in corresponding recesses, the holding wall being stationarily fastened to the stationary tool part and projecting beyond the mold joint in a direction toward the liftable tool part by at least half the diameter of the pull rod.
Because of the central arrangement and the linking of the pull rods in the area of the mold joints, the pull rods are relieved from moments during a tensile force load. This relieving of moments, in turn, permits the constructional detachment of the working cylinder from the bearing base plate so that different, particularly sloped spatial positions of the working cylinders may be permitted. The constructional detachment of the working cylinders from the base plate also permits the exchangeable coupling and the universal use of the working cylinders on different IHU-tools which are used alternately so that now, in the case of a retooling of the device to the production of a different hollow body, only the die parts carrying the impression have to be changed and the working cylinders may remain in the device. The number of parts which have to be exchanged during a retooling can therefore be reduced considerably.
Although it is known from German Patent Document DE 43 20 236 C1 to hold, in the case of devices for producing hollow bodies according to the IHU-process, the metal forming slides so that they can be adjusted in space relative to one another with respect to their axial position and with respect to their point of application, a displacement construction is shown for this purpose which has a high-expenditure design, is flexible under a load and is not satisfactory in practice.
These and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.